src/test/ui/nullable-pointer-iotareduction.rs

   1 // run-pass
   2
   3 #![feature(box_syntax)]
   4
   5 // Iota-reduction is a rule in the Calculus of (Co-)Inductive Constructions,
   6 // which "says that a destructor applied to an object built from a constructor
   7 // behaves as expected".  -- https://coq.inria.fr/doc/language/core/conversion.html#iota-reduction
   8 //
   9 // It's a little more complicated here, because of pointers and regions and
  10 // trying to get assert failure messages that at least identify which case
  11 // failed.
  12
  13 enum E<T> { Thing(isize, T), Nothing((), ((), ()), [i8; 0]) }
  14 impl<T> E<T> {
  15     fn is_none(&self) -> bool {
  16         match *self {
  17             E::Thing(..) => false,
  18             E::Nothing(..) => true
  19         }
  20     }
  21     fn get_ref(&self) -> (isize, &T) {
  22         match *self {
  23             E::Nothing(..) => panic!("E::get_ref(Nothing::<{}>)",  stringify!(T)),
  24             E::Thing(x, ref y) => (x, y)
  25         }
  26     }
  27 }
  28
  29 macro_rules! check_option {
  30     ($e:expr, $T:ty) => {{
  31         check_option!($e, $T, |ptr| assert_eq!(*ptr, $e));
  32     }};
  33     ($e:expr, $T:ty, |$v:ident| $chk:expr) => {{
  34         assert!(None::<$T>.is_none());
  35         let e = $e;
  36         let s_ = Some::<$T>(e);
  37         let $v = s_.as_ref().unwrap();
  38         $chk
  39     }}
  40 }
  41
  42 macro_rules! check_fancy {
  43     ($e:expr, $T:ty) => {{
  44         check_fancy!($e, $T, |ptr| assert_eq!(*ptr, $e));
  45     }};
  46     ($e:expr, $T:ty, |$v:ident| $chk:expr) => {{
  47         assert!(E::Nothing::<$T>((), ((), ()), [23; 0]).is_none());
  48         let e = $e;
  49         let t_ = E::Thing::<$T>(23, e);
  50         match t_.get_ref() {
  51             (23, $v) => { $chk }
  52             _ => panic!("Thing::<{}>(23, {}).get_ref() != (23, _)",
  53                        stringify!($T), stringify!($e))
  54         }
  55     }}
  56 }
  57
  58 macro_rules! check_type {
  59     ($($a:tt)*) => {{
  60         check_option!($($a)*);
  61         check_fancy!($($a)*);
  62     }}
  63 }
  64
  65 pub fn main() {
  66     check_type!(&17, &isize);
  67     check_type!(box 18, Box<isize>);
  68     check_type!("foo".to_string(), String);
  69     check_type!(vec![20, 22], Vec<isize>);
  70     check_type!(main, fn(), |pthing| {
  71         assert_eq!(main as fn(), *pthing as fn())
  72     });
  73 }